1. Field of the Invention
This invention relates to an X-ray CT(computer tomography) apparatus, an X-ray detector and a method of manufacturing an X-ray detector.
2. Description of the Related Arts
In an X-ray CT apparatus, X-rays are emitted from an X-ray tube and are formed into a fan-like shaped X-ray beam by a collimator.
The X-ray tube, and a circular arc like detector and a collimator facing the X-ray tube are rotated around a target object.
The detector receives X-rays which have passed through the target object and obtains X-ray information as a signal from the received X-ray. An X-ray tomography picture of the target object is obtained by processing the X-ray information by using a computer.
Some of the X-rays emitted from the X-ray tube travel straight and penetrate the target object, and other X-rays are scattered by the target object.
The collimator has a collimator board provided in front of the detector. The collimator removes the scattered X-rays incident from the oblique direction. The collimator passes the X-rays which have traveled straight and penetrated the target object. The collimator board forms an X-ray shield wall in front of the detector. The detector has detection elements which are arranged in a one- or two-dimensional manner. FIG. 17 and FIG. 18 show perspective views of known collimators and X-ray detectors. FIG. 17 shows a collimator having a collimator board arranged in the one-dimensional manner. FIG. 18 shows a collimator having a collimator board arranged in the two-dimensional manner.
In FIG. 17, collimator boards 50, 51 are shown together with a detection element array 52. In FIG. 18, a collimate board 53 is shown together with a detection element array 54.
The collimator arranged in one-dimension removes scattered X-rays in a certain direction, for example, a channel direction. The collimator arranged in two dimensions removes scattered X-ray in two directions, for example, channel and slice directions.
When manufacturing the X-ray detector, a collimator and an X ray detector are needed to be assembled with sufficiently accurate positioning.
This is because the collimator and the X ray detector are manufactured separately as shown in FIG. 17 or FIG. 18.
The collimator may contain a plurality of Mo(Molybdenum) boards. The X-ray detector may contain a reflector. In the assembling process, it is necessary to position the collimator and the X-ray detector with a small gap in a rotating direction.
But it takes considerable time to carry out the assembling process with high positioning accuracy.